It is known in the metallurgical industry to introduce solid metal additives to baths of molten base metals to provide alloyed compositions thereof having mechanical and chemical properties different from those of the base metals alone. For example, it is known to add manganese to molten aluminum in the form of a manganese-aluminum alloy to provide increased strength to wrought aluminum products produced therefrom. Other additive metals which have been utilized in the metallurgical industry to modify the mechanical and chemical properties of a variety of base metal include chromium, tungsten, molybdenum, vanadium, iron, cobalt, copper, nickel and the like.
It has been common practice to introduce these solid metl additives into baths of molten base metals in the form of solid preformed alloys of said metal additives and the base metals. However, the use of such solid preformed alloys has not been entirely satisfactory. For example, a solid preformed alloy of an additive and base metal is relatively expensive to produce. In addition, such a preformed alloy is quite often characterized by a poor dissolving rate and a tendency to cause a large and highly undesirable temperature drop in the bath of molten base metal to which it is added. To overcome these drawbacks it has been proposed to introduce the desired metal additive into the bath of molten base metal to be treated in the form of an uncompacted or compacted blended mixture of the additive and base metal. See, for example, U.S. Pat. No. 3,592,637. According to the disclosures in this patent, the blended mixtures comprise a "principal material", i.e., the additive metal desired to be alloyed with a base metal in a molten bath of the latter to modify some particular property thereof, and a "solution promoter" material which generally consists of the base metal itself. The advantages of using blended mixtures for making metal additions to baths of molten base metals rather than the previously employed preformed alloys thereof are disclosed as including better economics, faster dissolving rates for the additive metal, and little or no tendency of the blended mixtures to cause temperature drops in the bath of molten base metal upon their addition thereto.
Further, in accordance with said U.S. Pat. No. 3,592,637, it is disclosed that the blended mixtures of two or more finely divided metals can be added to the bath of molten base metal in the form of either uncompacted confined mixtures or as pressed compacts or pellets. In this regard, the patent still further discloses that the form most preferred is that of pressed compacts or pellets. However, in preparing pressed compacts or pellets of the above described blended mixtures, at least two problems are encountered. One is that during the compacting operation the metals comprising the blended mixture have a tendency to segregate one from the other such that the resultant compact or pellet is not of uniform distribution. The second problem is associated with the abrasive characteristics of the blended mixture and the resultant damage that such abrasive characteristic has on process equipment during the forming of said compressed compacts or pellets.
To overcome the above described problems, practice has been to add a processing aid, such as mineral oil, to the blended mixture of metals. However, while the addition of mineral oil to the blended mixture of metals does improve the processibility of the mixture, the use of mineral oil has not been entirely satisfactory. For example, experience has shown that when compacted or molded articles of blended mixtures of metals containing mineral oil are added to baths of molten base metal, the mineral oil readily undergoes decomposition with the generation of flames and the formation of dense black smoke. Neither flame generation nor smoke formation is desirable from a safety and environmental standpoint. Therefore, a need exists for a different group of processing aids which does not exhibit the undesirable characteristics of mineral oil but does exhibit a desirable characteristic thereof, namely the characteristic of not adversely affecting the dissolution rate of the blended mixture when added to the bath of molten base metal.